In recent years, image forming apparatus is spread which can mount a toner cartridge having RFID tag and can manage toner remainder amount. In such conventional image forming apparatus, the RFID tag is furnished on the upper part of the toner cartridge, and a RFID antenna is furnished in a position which is on an upper cover of the image forming apparatus and faces to the RFID tag (refer to FIG. 6 of Patent Document 1). On the basis of such structure, the RFID tag and the RFID antenna communicate in radio form, and an management of toner remainder amount is executed.
Patent Document 1: Japan patent publication 2006-267528.
However, in such image forming apparatus, there is a problem, that is, because a distance precision or a relative position precision between the RFID tag and the RFID antenna is not achieved, communication error easily occurs. In particular, in such image forming apparatus comprising image forming units of four colors of Y (Yellow), M (Magenta), C (Cyan), K (Black), in the case to alternate color print and monochrome print, except the image forming unit of K color, the other image forming units of other three colors shift up and down, because of such repeated operations, it is difficult to keep precision of distance or relative position.